.. _old_animation-strip_chart_demo:

old_animation example code: strip_chart_demo.py
===============================================

[`source code <strip_chart_demo.py>`_]

::

    """
    Emulate an oscilloscope.  Requires the animation API introduced in
    matplotlib 0.84.  See
    http://www.scipy.org/wikis/topical_software/Animations for an
    explanation.
    
    This example uses gtk but does not depend on it intimately.  It just
    uses the idle handler to trigger events.  You can plug this into a
    different GUI that supports animation (GTKAgg, TkAgg, WXAgg) and use
    your toolkits idle/timer functions.
    """
    import gobject
    import matplotlib
    matplotlib.use('GTKAgg')
    import numpy as np
    from matplotlib.lines import Line2D
    
    
    class Scope:
        def __init__(self, ax, maxt=10, dt=0.01):
            self.ax = ax
            self.canvas = ax.figure.canvas
            self.dt = dt
            self.maxt = maxt
            self.tdata = [0]
            self.ydata = [0]
            self.line = Line2D(self.tdata, self.ydata, animated=True)
            self.ax.add_line(self.line)
            self.background = None
            self.canvas.mpl_connect('draw_event', self.update_background)
            self.ax.set_ylim(-.1, 1.1)
            self.ax.set_xlim(0, self.maxt)
    
        def update_background(self, event):
            self.background = self.canvas.copy_from_bbox(self.ax.bbox)
    
        def emitter(self, p=0.01):
            'return a random value with probability p, else 0'
            v = np.random.rand(1)
            if v>p: return 0.
            else: return np.random.rand(1)
    
        def update(self, *args):
            if self.background is None: return True
            y = self.emitter()
            lastt = self.tdata[-1]
            if lastt>self.tdata[0]+self.maxt: # reset the arrays
                self.tdata = [self.tdata[-1]]
                self.ydata = [self.ydata[-1]]
                self.ax.set_xlim(self.tdata[0], self.tdata[0]+self.maxt)
                self.ax.figure.canvas.draw()
    
            self.canvas.restore_region(self.background)
    
            t = self.tdata[-1] + self.dt
            self.tdata.append(t)
            self.ydata.append(y)
            self.line.set_data(self.tdata, self.ydata)
            self.ax.draw_artist(self.line)
    
            self.canvas.blit(self.ax.bbox)
            return True
    
    
    from pylab import figure, show
    
    fig = figure()
    ax = fig.add_subplot(111)
    scope = Scope(ax)
    gobject.idle_add(scope.update)
    
    show()
    

Keywords: python, matplotlib, pylab, example, codex (see :ref:`how-to-search-examples`)